Electromagnet with armature



2 Sheets-Sheet 1 INVENToRs ,4free/Vix Feb. 17, 1948. J. D. BURKE Erm.

ELECTROMAGNET WITH ARMATURE Filed Oct; 1l, 1943 [Imm-5D. 50e/f5, Fa/.24

Feb. 17, 1948. J, D, BURKE 'Er/ 2,436,354

ELEcTnoMAGNE-r WITH MATURE AFiled Oct. 1l, 1943 2 Sheets-Sheet 2 Fa/ LEPA. Ceco/f5, IN VEN TOR5 Arroz/Vix Patented Feb. 17, 1948 UNITED STATESPATENT OFFICE ELECTROMAGNET WITH ARMATURE Application October 11, 1943.Serial No. 505,712

(Cl. F15-336) 18 Claims.

Our invention relates generally to electromagnets and particularly to amagnet in which the armature is subjected to both repellent andattractive forces, and hence may be referred to as a push-pull magnet.

It is an object of our invention to provide an electromagnet in whichsubstantially uniform power is exerted upon the armature during itsentire movement, resulting in a more rapid and positive action than ispossible with conventional types of magnets.

Another object of our invention is to provide an electromagnet which hasconsiderably more power for a given number of ampere turns than othertypes of magnet, and which has a relatively short flux path with aminimum of flux leakage.

A further object of our invention is to provide an electromagnet havinga balanced armature which is subjected to repellent and attractiveforces at each end thereof, to thereby increase its power.

An advantage of our invention is the ability of our electromagnet tooperate satisfactorily under the most adverse conditions of vibrationand shock such as encountered in aircraft and other vehicles. i

Another advantage of our electromagnet is the provision of increasedarmature movement without the sacrifice of contact power which makes itespecially valuable in relays where maximum contact dependability isrequired.

When used in a relay, one form of our invention provides a doublebreakin the control circuits, thereby increasing the arc-rupturingability when heavy currents are interrupted. Consequently, a relay ofthis type is capable of high altitude operation without vacuum seals.

These and other objects and advantages of our invention will becomeapparent from the follow- Lng description of preferred forms thereofillus- :rated in the accompanying drawings in which,

Fig. 1 is a top plan view of our invention employing one type ofarmature,

Fig. 2 is a vertical cross-section of the electronagnet shown in Fig. 1.

Fig. 3 is a perspective of the core and armature )f the magnet shown inFigs. 1 and 2,

Fig. 4 is a top plan view of an electromagnet employing a balancedarmature,

Fig. 5 is a vertical cross-section of the electronagnet of Fig. 4,

Fig. 6 is a perspective view of the core and irmature of the magnetshown in Figs. 4 and 5,

7 is a vertical cross-section of a form of our invention wherein boththe core and armature are movable,

Fig. 8 is an elevational detail of the armaturecore assembly of Fig. 7,

Fig. 9 is a perspective view of the armaturecore assembly of Figs. 7 and8, and

Fig. 10 is a. vertical cross-section of a magnet similar to that shownin Fig. 5 but omitting the axial core.

Referring now to the drawings and particularly to Figs. 1, 2 and 3thereof, the numeral I0 indicates a solenoid preferably wound on a spoolof suitable non-magnetic material comprising a central tube II havingupper and lower face plates I2 and I3 secured thereto. A core I4 whichis preferably taperedas shown, and provided with a pair of ears l5 andI6 at its lower end is axially disposed in the solenoid and securedwithin the tube I I in any convenient man ner, the core being preferablyslightly longer than the tube II so as to extend a little above theupper end thereof. An armature I'l which is also preferably taperedslightly is pivotally mounted at its lower end on a pin extendingbetween the ears I5 and I6 of core I4. As seen best in Fig. 2, thearmature I1 is free to move from position A to position B in response tothe magnetic forces created by energization of the solenoid I0.

A yoke I8 of suitable magnetic material preferably formed as a U issecured to the upper and lower plates I2 and I3 of the solenoid spool soas to provide a low-reluctance flux path around the outside of thesolenoid. The lower leg of the yoke I8 is preferably separated from thecore I4 by a slight air space or a layer of non-magnetic material so asto interrupt the magnetic path. The upper leg of the yoke I8 ispreferably formed with a central cut-away portion providing a centrallydisposed auxiliary pole portion I9 which confronts the upper end of thearmature Il, and a pair of extending fingers 20 and 2| lying on oppositesides of the core and armature. By this formation of the upper leg ofthe yoke I8 an improved flux path is created which minimizes leakage andfacilitates operation of the magnet.

The armature I1 is normally urged against the core I4, i. e., toposition A, by suitable spring means, such for example as the coilspring 22 extending between pin 23 on plate I2 and a pin 24 on armatureIl. The upper end of the armature may if desired have a contact 25thereon secured in a hole 26 provided for that purpose. It will beunderstood of course that the armature il can be made of various lengthsfor various purposes,

and can have diiferent types of contacts thereon.

When an electric current is passed through the solenoid I it willpolarize both core I4 and armature I'I, which will of course assume thesame polarities, for example as illustrated in Fig. 2 wherein the upperends of the core and armature are indicated by the letter N for northpoles, and the letter S for south poles. The yoke IB will also bepolarized but its upper end or pole piece I9 will assume a polarityopposite to that of the upper end of the armature and core. Assuming thearmature to be in its normal position against the core Il, it will beimmediately apparent that since the upper ends of the armature and coreare oi' like polarity the armature will be repelled by the core, andsince the polarities of the armature and the yoke pole piece I9 are 0P-posite, the armature will be attracted to the pole piece I9. Thearmature is thus both pushed and pulled from position A to position B,and since magnetic force varies inversely with the distance between thepoles, the repellent force between the core and the armature will bemaximum at the start of the armature movement, while the attractiveforce exerted on the armature by the yoke pole I9 will be a minimumiatthe start. However, as the armature moves farther away from the core Iland approaches the pole I9 the repellent force decreases while theattractive force increases, so that the total force exerted on thearmature is substantially uniform throughout its.

entire stroke. As soon as the solenoid is de-energized, the spring 22will of course return the armature to its normal position A.

Referring now toFigs. 4, 5, and 6 illustrating the balanced amature typeof our invention, the numerals III, Il. I2, and I3 again denote asolenoid, a spool tube, and top and bottom spool faces, respectively. Inthis form of our invention, however, the core is Z-shaped and c'omprisesan upper pole piece 30. an offset lower pole piece 3| and a centralcross bar 32 connecting the two pole pieces as indicated, the cross barbeing preferably formed with a slot in which an armature comprisingupper portion 33 and lower portion -34 is pivoted on a pin 35. The coreis preferably secured within the tube II so that the upper pole piece 30Arests against one wall of the tube and the lower pole piece 3| restsagainst the opposite wall oi' the tube II, the ends of the pole piecesprotruding slightly beyond the walls of the tube.

A yoke 36 which may be similar to yoke I8 is secured about the solenoidin its outer magnetic path and provides a central pole piece 31confronting the upper portion 33 of the armature as indicated. The lowerleg of the yoke 36 is magnetically insulated from the lower pole pieceof the core as before. A similar yoke 38 is mounted on the other side ofthe solenoid and has its lower leg formed similar to the upper leg ofthe yoke 36 and provided with a central pole piece 39.

The balanced armature is normally held with its two ends against theirrespective core pieces by suitable means such as spring 40 attached to apin 4I on the upper end of the armature, or by any other convenientmeans. Assuming the armature in its normal position A, energization ofthe solenoid polarizes both the core and the armature as before. withthe upper end having one polarity, north for example, and the lower endshaving opposite polarity. The yokes 36 and 38 will also be polarizedwith their upper legs having south polarity and their lower legs, northpolarity when the current travels in the appropriate direction.- Asbefore, the upper end of the armature is repelled by the upper polepiece Sil of the core and is attracted by the pole piece Si of the yoke36 to give a push-pull action to the armature. Similarly the lower endof the armature which has south polarity is repelled by the lower polepiece 3l of the core and is attracted by thellower pole piece 39 of theyoke 38, thus doubling the force exerted on the armature. Since thearmature is preferably balanced at its center, it will be apparent thatit will be very stable and relatively insensitive to outside forces.When the solenoid is de-energized the armature will of course bereturned to its normal rest position A by the resilient means dil.

Referring now to Figs. 7 9, inclusive, the numeral It again indicates asolenoid wound on a spool comprising a central tube il and upper andlower face plates I 2 and I 3 respectively. A core I4 and an armature ilare pivotally connected at their lower ends by means of a pair of earsI5 and I6 having a pin extending between them. In this case, however,both core It and armature Il are mounted for movement, and are normallyurged together by suitable resilient means such for example as thespring 22 which centers the core and armature in the tubular portion IIof the solenoid-spool. 'I'he armature I 'l carries an externally facingcontact 25 as before. and the core I4 also carries a contact, which isindicated by the numeral 2li-a.

In the form shown in Fig. 7 yokes 36 and 38 are provided which may besimilar to the yokes of like number in Fig. 5, the yoke 36 providing apole piece 31 confronting the upper end of armature Il, and the yoke 38providing a pole piece 31a confronting the movable core I4.

In the operation of this form of our invention the core I4 and armatureI'l are similarly polarized by energization of the solenoid,l and in theexample shown, their upper ends assume north polarity, thereby repellingeach other and causing both of the axially disposed members I4 and Il tomove outwardly against the urging of the spring 22. In the magnet ofFig. 7 this movement of the members I4 and I1 is facilitated by the polepieces 31 and 31a which assume south polarity and therefore attracttheir adjacent movable members. We thus get push-pull operation with theadditional advantage of having both the core I4 and the armature I1movable to make contact with suitably placed switch pieces (not shown)or for other purposes. Where the extra force furnished by the auxiliarypole pieces is not desired, they may be omitted. By the construction ofFig. 7 we secure a very fast acting magnet which is particularlysuitable for relays sub- Ajected to large accelerative forces, such asencountered in aircraft operation. By using the core and armature toprovide a double contact in the same circuit. one of them will always beadditionally urged to closed contact position by the accelerative forcesaffecting the magnet, so that if one contact is broken by suddenacceleration, the other one remains closed to keep the circuit frombeing broken.

Referring now to Fig. 10, the numeral I0 indicates a solenoid wound on aspool comprising tube Il and face plate I2 and I3. An armaturecomprising upper and lower portions 33 and 34 similar to that shown inFig. 5 is pivotally mounted on a pin 36 in a crossblock 32 fastenedwithin the tube II. A yoke 36' has an upper leg which provides a polepiece 31' confronting one face of the upper end of the armature, andadapted to assume a polarity opposite thereto when the solenoid isenergized. A second yoke 38' has a lower leg providing a pole piece 39'confronting the opposite face of the other end of the armature. Thispole piece also assumes a polarity opposite to that of its confrontingarmature face. In the example illustrated in Fig. the upper end 33 ofthe armature becomes a north pole while its lower end 34 becomes a southpole when the solenoid is energized. Consequently the upper yoke polepiece 3l becomes a south pole and the lower yoke pole piece assumesnorth polarity. By thus arranging the pole pieces in the outer magneticpath of the solenoid we secure a double pull on the balanced armatureand provide an electromagnet which is adapted for use where highsensitivity and stability but not excessve power are required.

From the foregoing description of various forms of our invention it isseen that we provide simple and eicient means of greatly increasing thepower of an electromagnet without increasing either its size or thecurrent required. Also, by placing the movable member or members insideof the solenoid, we insure that all magnetizing forces acting thereonare created by the same flux lines, thus eliminating the possibility ofunbalanced forces which tend to cause flux leakage. Furthermore, by theconstruction illustrated herein we are able to have a relatively shortflux path with consequent small leakage losses.

It will be understood of course that the electromagnet of our inventionhas a wide range of uses, and that While we have illustrated in detailvarious simple forms of our invention which are particularly well suitedfor relay and other uses, we do not mean to limit ourselves to thestructures shown, but rather intend that our invention shall be giventhe full scope defined by the appended claims.

We claim:

1. An electromagnet which includes: a solenoid; a pair of spaced apartunconnected stationary pole pieces, one disposed inside of said solenoidand the other on the outside of said solenoid but in the magnetic paththereof, said poles being arranged to assume opposite polarity; and anarmature pivotally mounted within said solenoid having an end movablebetween said poles and adapted to be polarized, whereby when saidsolenoid is energized said armature will be repelled by one andattracted by the other of said stationary poles.

2. An electromagnet which includes: a solenoid; a core axially disposedwithin said solenoid forming a pole piece at each end thereof; and anarmature axially disposed within said solenoid adjacent said core andpivotally mounted thereon for movement with respect thereto said pivotpoint being within said solenoid, whereby when said solenoid isenergized said core and armature will be similarly polarized causingsaid armature to move away from said core.

3. An electromagnet which includes: a solenoid; a core axially disposedwithin said solenoid forming a pole piece at each end thereof; anarmature axially disposed within said solenoid adjacent said core andpivotally mounted on said core for movement with respect thereto,whereby when said solenoid is energized said core and armature will besimilarly polarized causing said armature to move away from said core;and a yoke in the outside magnetic path of said solenoid with one endterminating adjacent the movable end of said armature and assumingopposite polarity thereto when said solenoid is energized. and the otherend thereof terminating adjacent the other end of said core butmagnetically insulated therefrom.

4. An electromagnet which includes: a solenoid; a core axially disposedwithin said solenoid forming a pole piece at each end thereof; anarmature axially disposed Within said solenoid adjacent said core andpivotally mounted on said core for movement with respect thereto,whereby when said solenoid is energized said core and armature will besimilarly polarized causing said armature to move away from said core;resilient means normally urging said armature against said core; and anexternal pole piece in the outside magnetic path of said solenoid withone end terminating adjacent the movable end of said armatuie andassuming opposite polarity thereto when said solenoid is energized, andthe other end thereof terminating adjacent the other end of said corebut magnetically insulated therefrom.

5. An electromagnet which includes: a solenoid; core means within saidsolenoid providing pole pieces at each end thereof, but displacedlaterally of each other; and an armature pivotally mounted in thecentral portion of said solenoid with its ends respectively adjacentsaid pole pieces, whereby said core and armature are polarized uponenergization of said solenoid to cause each end of said armature to berepelled by its adjacent pole piece, and to rotate on its pivotmounting.

6. An electromagnet which includes: a solenoid; core means within saidsolenoid providing pole pieces at each end thereof; and an armaturepivotally mounted in the central portion of said core with oppositefaces of its opposite ends respectively confronting said core pieces,whereby when said armature and core pieces are polarized by energizationof said solenoid, said confronting portions will have the same polarityto thereby exert a repellent force on each end of said armature torotate the same.

7. An electromagnet which includes: a solenoid; core means axiallypositioned in said solenoid and providing a north pole piece at one endthereof and a south pole piece at the other end thereof; and an armatureaxially positioned in said solenoid and providing northl and south polesat the opposite ends of said solenoid, said armature and core meansbeing disposed so that a line joining the core pole pieces will at alltimes intersect a line joining the armature pole pieces at an acuteangle, whereby upon energization of said solenoid and polarization ofsaid core and armature, the armature will be additively repelled at eachend thereof.

8. An electromagnet which includes: a solenoid; core means axiallypositioned in said solenoid and providing a north pole piece at one endthereof and a south pole piece at the other end thereof; an armatureaxially positioned in said solenoid and providing north and south polesat the opposite ends of said solenoid, said armature and core meansbeing disposed so that a line joining the core pole pieces will at alltimes intersect a line joining the armature pole pieces at an acuteangle, whereby upon energization of said solenoid and polarization ofsaid core and armature, the armature will be additively repelled at eachend thereof; and yoke means around said solenoid in the outside magneticpath thereof which provides auxiliary north and south 9 poles on eachend of said solenoid adapted to respectively attract each end of saidamature.

9. An electromagnet which includes: a solex noid; a Z-shaped memberdisposed within said solenoid axially thereof; and a second membersolenoid pivoted near its center on the cross-barl of said Z, both saidcore and amature adapted to be polarized when said solenoid isenergized, whereby said armature is additively repelled by the poles ofsaid core; and yoke means providing auxiliary `poles at opposite ends ofsaid solenoid to attract said armature.

1l. An electromagnet which includes a solenoid; an armature axially androtatably mounted within said solenoid; and means in the outsidemagnetic path of said solenoid forming pole pieces on opposite ends ofsaid solenoid confronting opposite faces of said armature, whereby uponenerglzation of said solenoid said pieces will assume polaritiesopposite to those assumed by the respective confronting faces of saidarmature to cause rotation thereof,

12. An electromagnet which includes: a solenoid; means associated withsaid solenoid in the magnetic path thereof providing pole pieces at eachend thereof, but displaced laterally of each other; and an armaturepivotally mounted within said solenoid with its ends respectivelyadjacent said pole pieces, whereby said armature and pole pieces arecooperatively energized upon energization of said solenoid to cause saidarmature to rotate on its pivot mounting.

13. An electromagnet which includes: a solel noid; means associated withsaid solenoid in the magnetic path thereof providing a north pole pieceat one end of said solenoid and a. south pole piece at the other endthereof; and an armature pivotally mounted within said solenoidandproviding north and south poles at the opposite ends of said solenoid,said armature and said pole pieces being disposed so that a line joiningsaid pole pieces will at all times intersect a line joining the armaturepoles at an acute angle. whereby upon energization of said armature andpole pieces, the armature will be rotated on its pivot mounting.

14. As an article of manufacture, a core-armature assembly for insertionin a solenoid, which comprises, a longitudinal core member, and alongitudinal armature member pivotally connected together intermediatetheir end faces and lying in substantial juxtaposition, whereby they maybe inserted into an open end of said solenoid and be similarly polarizedupon energization of said solenoid.

15. An electromagnet which includes: a solenoid; a Z-shaped memberdisposed within said solenoid axially thereof; a second member withinsaid solenoid pivoted near its center on the cross-bar of said Z, bothof said members being adapted to be polarized when said solenoid isenergized, whereby one of said members is additively repelled by thepoles of the other of said members; and yoke means providing auxiliarypoles at opposite ends of said solenoid.

16. An electromagnet which includes: a solenoid; an axially extendingpole piece rigidly mounted within said solenoid; an axially extendingarmature pivotally attached within said solenoid to said pole piece atone end of the latter whereby energization of -said solenoid causes likemagnetization of said armature and said pole piece; and an outer polepiece in the external magnetic circuit of said solenoid, whollyseparated from said axial pole piece and from said pivoted end of saidarmature, said outer pole piece being adapted to have magnetic polesinduced therein which are of opposite polarity to adjacent poles of saidaxial pole piece and said armature, whereby said axial pole piece isattracted to said outer pole piece but is immovable with respectthereto, while said armature is repelled by said axial pole piece andattracted by said outer pole piece when said solenoid is energized.

17. An electromagnet which includes: a solenoid; an axially extendingpole piece within said solenoid; an outer pole piece in the externalmagnetic circuit of said solenoid, wholly separated from said axial polepiece but adjacent one end of the latter; and an armature within saidsolenoid pivotally attached to said axial pole piece at the end thereofadjacent said outer pole piece, whereby energizing said solenoid inducesmagnetic elds of like polarity in said axial core and said armature,thereby urging said armature away from said axial pole piece andattracting said armature toward said outer pole piece.

18. An electromagnet which includes: asolenoid; an axially extendingpole piece rigidly mounted within said solenoid: an armature within saidsolenoid and substantially parallel thereto, pivotally attached to saidaxial pole piece at one end of the latter; and an outer pole piece inthe external magnetic circuit of said solenoid wholly separat-ed fromsaid axial pole piece but adjacent the latter at its point of pivotalattachment to said armature, said outer pole piece being adapted toattract the free end of said armature so that the latter bears againstit, whereby energization of said solenoid induces magnetic poles of likepolarity in said axialpole piece and said armature, and magnetic polesof unlike polarity in said armature and the adjacent portion of saidouter pole piece, thereby causing said armature to be repelled from saidaxial pole piece and attracted toward said outer pole piece.

JAMES D. BURKE. FULLER. A. CROOKS.

ille of this patent:

UNITED STATES PATENTS Number Name Date 969,345 Culver Sept. 6, 19101,726,424 Y Churcher Aug. 27, 1929 749,399 Pickard Jan. 12, 19041,262,233 Murray Apr. 9, 1918 05 1,333,247 Cummings Mar. 9, 19201,547,772 Moore July 28, 1925 1,624,476 Cummings Apr. 12, 1927 1,680,667Curtis Aug. 14, 1928 FOREIGNVPATENTS Number Country Date 175,083 GreatBritain Feb. 16, 1922 697,708 Germany Nov. 6, 1940 76 47,326 AustriaApr. 10, 1911

